Neurological impairment, such as spinal cord injury (SCI), can occur in people of any age, and is often caused by injuries sustained in accidents associated with motor vehicles, firearms, sports injuries, and the like. Many of the individuals who sustain such injuries are young male adults between the ages of 16 and 30 who, up to the point of the accident, have lead active and healthy lives.
In the USA, the prevalence of neurological impairment resulting from SCI is estimated at between 712 and 906 per million with the incidence of SCI being calculated at between about 30 and 40 per million. It is widely recognised that SCI has a large impact on society in general and is a sudden and irreversible change to an individual's quality of life.
In order to define SCI, it should be understood that an SCI is a traumatic lesion to the spinal cord and the associated nerves. Thirty-one spinal nerves originate from the spinal cord and can be grouped as follows: 8 cervical (C1 to C8), 12 thoracic.(T1 to T12), 5 lumbar (L1 to L5), 5 sacral (S1 to S5) and 1 coccygeal. An injury to the spinal cord can result in varying degrees of impairment depending on where and to what extent the spinal cord is injured. In general, the higher up on the spinal cord the injury, the more severe the resulting impairment.
People suffering from an SCI are essentially categorised into two main groups: tetraplegics and paraplegics.
Tetraplegics are individuals who have sustained an injury to one of the eight cervical segments of the spinal cord, C1 to C8. Such an injury results in impaired use of the arms and hands as well as the legs. A person who has suffered such an injury generally experiences significant loss of sensation and volitional body movement as well as the loss of volitional bladder and bowel control. Many tetraplegics may also have loss of psychogenic and impaired reflex erections.
Paraplegics are individuals who have sustained an injury at the thoracic level, T1 to T12. These individuals usually have sensation and volitional control over their upper limbs, but have lost sensation and control of their lower limbs and bladder and bowel control, as well as erection problems in males.
Due to SCI individuals being unable to control bladder function, individuals must regularly self cathertise. This procedure is problematic, especially for females, and can result in an increase in the incidence of urinary tract infections. Still further, persons suffering from SCI must often undertake lengthy bowel evacuation procedures using, for instance, digital evacuation. SCI patients are also prone to secondary medical problems, such as pressure sores, osteoporosis, muscular atrophy in the lower limbs, muscle spasticity, deep vein thrombosis, cardiovascular disease and depression. Pressure sores are caused by the occlusion of blood flow during sitting and lying. They are a major health problem which may require surgery to repair and months of rehabilitation including requiring the patient to remain lying on their abdomen for an extended period of time.
Therefore, whilst restoration of bladder and bowel control is a primary need of SCI individuals, reduced incidence of pressure sores is also highly needed. This, together with the ability to exercise and stand and step, are functions that would greatly improve the quality of life of SCI individuals.
It is therefore evident that a large proportion of the population who have an SCI would benefit from a device that would be able to assist in the at least partial restoration of such lost functionality, in particular bowel and bladder function, erectile function, the reduction in the incidence of pressure sores and the provision of exercise and upright mobility. Various systems have been proposed by numerous organisations to deal with one or other of the functions that have been lost to SCI individuals.
The Applicant has previously developed a multi-purpose, functional electrical stimulation system. That system is described in International Patent Application PCT/AU03/00044, and is used to stimulate a number of sites in a patient's body using a single stimulator unit.
The stimulator unit is, in use, implanted in a costal region of the patient's body and may be required to stimulate regions such as the upper or lower extremities of the patient's body and the sacral and/or thoracic regions of the patient's spinal cord. Each site has multiple stimulation points which necessitates the leading of numerous electrical leads from the location of the stimulator unit to the relevant site.
In addition, it may occur that, at a later date, additional stimulation points at the site need to be stimulated which may necessitate the leading of additional electrical leads from the location of the stimulator unit to the stimulation point of the site.